docs: def format_url(self, url, **kwargs):
          # type: (str, Any) -> str
          """Format request URL with the client base URL, unless the
          supplied URL is already absolute.
  
          :param str url: The request URL to be formatted if necessary.
          """
          url = url.format(**kwargs)
          parsed = urlparse(url)
          if not parsed.scheme or not parsed.netloc:
              url = url.lstrip('/')
              base = self.config.base_url.format(**kwargs).rstrip('/')
              url = urljoin(base + '/', url)
          return url